In issue 37834, I posted a suggest implementation of win32_xstat_impl that included the following snippet of code:

        if (!GetFileInformationByHandle(hFile, &fileInfo)) {
            error = GetLastError();
            if (error != ERROR_INVALID_PARAMETER &&
                error != ERROR_INVALID_FUNCTION &&
                error != ERROR_NOT_SUPPORTED) {
                retval = -1;
                goto cleanup;
            }
            /* Volumes and physical disks are block devices, e.g.
               \\.\C: and \\.\PhysicalDrive0. */
            memset(result, 0, sizeof(*result));
            result->st_mode = 0x6000; /* S_IFBLK */
            goto cleanup;
        }

This is meant to handle the above errors. We know we have FILE_TYPE_DISK. If GetFileInformationByHandle fails with one of the above error codes, then we must have a disk or volume device without a mounted file-system device. This should be reported as a block device.

However it was changed in the final version as follows:

        if (!GetFileInformationByHandle(hFile, &fileInfo)) {
            switch (GetLastError()) {
            case ERROR_INVALID_PARAMETER:
            case ERROR_INVALID_FUNCTION:
            case ERROR_NOT_SUPPORTED:
                retval = -1;
                goto cleanup;
            }
            /* Volumes and physical disks are block devices, e.g.
               \\.\C: and \\.\PhysicalDrive0. */
            memset(result, 0, sizeof(*result));
            result->st_mode = 0x6000; /* S_IFBLK */
            goto cleanup;
        }

Now it's failing on the errors that should be handled, and succeeding on all other errors that should fail. If we want to use a switch statement here, I suggest the following:

        if (!GetFileInformationByHandle(hFile, &fileInfo)) {
            switch (GetLastError()) {
            case ERROR_INVALID_PARAMETER:
            case ERROR_INVALID_FUNCTION:
            case ERROR_NOT_SUPPORTED:
                /* Volumes and physical disks are block devices, e.g.
                   \\.\C: and \\.\PhysicalDrive0. */
                memset(result, 0, sizeof(*result));
                result->st_mode = 0x6000; /* S_IFBLK */
                goto cleanup;
            }
            retval = -1;
            goto cleanup;
        }

New changeset 772ec0fad57412daa53d16d7019b6b2fe6e94942 by Steve Dower in branch 'master':
bpo-38030: Fix os.stat failures on block devices on Windows (GH-15681)
https://github.com/python/cpython/commit/772ec0fad57412daa53d16d7019b6b2fe6e94942

New changeset cad7abf8abe657b696b9c8deb4b727e0cefaf36d by Miss Islington (bot) in branch '3.8':
bpo-38030: Fix os.stat failures on block devices on Windows (GH-15681)
https://github.com/python/cpython/commit/cad7abf8abe657b696b9c8deb4b727e0cefaf36d